blowfish.c

#include <err.h>

#include "blowfish.h"

const char B64[] =
"./0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";


/* decode base64 string */
    static uint32_t
base64dec (char c)
{
    size_t i;

    for (i = 0; i < 64; i++)
        if (B64[i] == c)
            return i;

    return 0;
}

    static uint32_t
load32_be (const void *p)
{
    const unsigned char *in = p;
    return (uint32_t) in[0] << 24 |
        (uint32_t) in[1] << 16 | (uint32_t) in[2] << 8 | (uint32_t) in[3] << 0;
}

    static void
store32_be (void *p, uint32_t v)
{
    unsigned char *out = p;
    out[0] = v >> 24;
    out[1] = v >> 16;
    out[2] = v >> 8;
    out[3] = v >> 0;
}

/* Returned string must be freed when done with it! */
    int
encrypt_string (const char *key, const char *str, char *dest, int len)
{
    BF_KEY bf_key;

    if (!key || !key[0])
        return 0;

    BF_set_key (&bf_key, strlen (key), (const unsigned char *) key);

    while (len > 0)
    {
        const size_t blocksize = len < 8 ? len : BF_BLOCK;
        unsigned char block[BF_BLOCK] = { 0 }; /* pad with zero */
        uint32_t v;
        size_t i;

        memcpy (block, str, blocksize);
        BF_ecb_encrypt (block, block, &bf_key, BF_ENCRYPT);

        for (v = load32_be (block + 4), i = 0; i < 6; ++i)
        {
            *dest++ = B64[v & 0x3f];
            v >>= 6;
        }

        for (v = load32_be (block + 0), i = 0; i < 6; ++i)
        {
            *dest++ = B64[v & 0x3f];
            v >>= 6;
        }

        len -= blocksize;
        str += blocksize;
    }

    *dest++ = 0;
    return 1;
}

    int
decrypt_string (const char *key, const char *str, char *dest, int len)
{
    BF_KEY bf_key;
    uint32_t v;
    size_t i;

    /* Pad encoded string with 0 bits in case it's bogus */
    if (!key || !key[0]) {
        errx(1, "!key || !key[0]");
        return 0;
    }

    /* length must be a multiple of BF_BLOCK encoded in base64 */
    if (len % (BF_BLOCK * 6 / 4) != 0) {
        warnx("len %% (BF_BLOCK * 6 / 4) != 0: %d, %s", len, str);
        len -= len % (BF_BLOCK * 6 / 4);
    }

    BF_set_key (&bf_key, strlen (key), (const unsigned char *) key);
    while (len > 0)
    {
        unsigned char block[BF_BLOCK] = { 0 };

        for (i = v = 0; i < 6; ++i)
            v |= base64dec (*str++) << (i * 6);
        store32_be (block + 4, v);

        for (i = v = 0; i < 6; ++i)
            v |= base64dec (*str++) << (i * 6);
        store32_be (block + 0, v);

        BF_ecb_encrypt (block, block, &bf_key, BF_DECRYPT);

        memcpy (dest, block, BF_BLOCK);
        dest += BF_BLOCK;
        len -= BF_BLOCK * 6 / 4;
    }

    *dest++ = 0;
    return 1;
}